Their scheme situates them on the underside of the social order, figuring as the legacy of the illegitimate Mannon line. Thus, in poisoning Ezra, Brant fears that he has inherited the cowardice of his father. Note also how Christine retrieves the name of the poison from her own father's medical textbooks. Her treachery, turning medicine into poison, involves the abuse and appropriation of paternal authority.
As Christine triumphantly proclaims, the father's murder seals their illicit union. Thus Christine's displays her violently incestuous desire to eliminate the father from the Oedipal triangle and be alone with her son. Brant is mistaken in fearing Christine loves him as another Ezra. As she ingenuously assures him, she loves him because he reminds her of Orin. Within the Oedipal drama, Christine figures as the mother who prizes her son as that which makes good on her castration. Thus Lavinia's taunt that soon Christine will be too old for her boyish lover devastates her.
On her part, Lavinia takes her mother as rival. As Christine sneers, Lavinia has always schemed to take her place, to become her father's wife and son's mother. The extent of her identification with Christine, one founded in the hate-filled belief that Christine stands in the place that is properly hers, will become chillingly clear in the subsequent plays.
As her closing exclamation makes clear, Christine would ensure her union against the threat of the Island girls. For her, the native functions as a cipher of sexual pleasure and excess. Her exclamation that closes the scene brims with envy. Christine is tormented by the fantasy of the pleasures that would be accessible only to the foreign other.